An adjustable damping valve device comprising a pre-stage valve and a main stage valve is known from U.S. Pat. No. 9,297,437. Further, an emergency operation valve which occupies an emergency operation position during an outage of the power supply for an actuator of the damping valve device is connected in series with the pre-stage valve. At least one pressure relief valve which opens in the event of overpressure in a control space of the damping valve device and accordingly determines a maximum damping force setting is in turn connected in parallel with the emergency operation valve. Accordingly, the damping valve device comprises at least four individual valves which must be adapted to one another and which require a substantial manufacturing effort.
The emergency operation valve comprises an annular emergency operation valve body which is preloaded by an emergency operation valve spring on a valve seat surface which is separate with respect to the pre-stage valve.
U.S. Pat. No. 9,310,810 discloses an alternative solution. The at least one pressure relief valve is likewise arranged in the emergency operation valve. For this reason, small pressure relief valves which screw into the emergency operation valve, for example, can be provided taking into account the required installation space. Pressure relief valves of this kind are available as modular units and are comparatively inexpensive. However, owing to the small construction, they are comparatively sensitive with respect to manufacturing tolerances, e.g., in the closing spring. While this problem can be compensated with an adjustable supporting surface for the closing spring, the achievable volume flows through an individual pressure relief valve are comparatively small. Consequently, a plurality of pressure relief valves must be provided, which increases assembly costs.
It is thus an object of the present invention to provide an adjustable damping valve device with an emergency operation function which has a simpler overall construction compared with the prior art.